Generally, a secondary battery refers to a rechargeable battery, while a primary battery refers to a non-rechargeable battery. Secondary batteries are widely used for electronic devices such as cellular phones, notebook computers, video cameras, electric vehicles, or the like. In particular, a lithium secondary battery recently has a higher capacity in comparison to nickel-cadmium batteries or nickel hydrogen batteries and a high energy density per unit weight. For this reason, lithium secondary batteries are being utilized more and more.
The lithium secondary battery includes an electrode assembly in which a cathode plate coated with a cathode active material and an anode plate coated with an anode active material are disposed with a separator interposed between them, and the electrode assembly is contained and sealed in an exterior material together with an electrolyte.
The cathode active material generally employs lithium metal oxides such as LiMn2O4 or LiCoO2, and the anode active material generally employs a carbon material.
In particular, in case of the anode active material, a lithium metal was used in an early stage, but since lithium has low reversibility and low safety, a carbon material is widely used at present. The carbon material has a small volume change, excellent reversibility and good price, though its capacity is small in comparison to a lithium metal.
However, as lithium secondary batteries are used more and more, high-capacity lithium secondary batteries are demanded more and more, and accordingly a high-capacity anode active material capable of substituting a small-capacity carbon material is also demanded. To meet such demands, there are many attempts to use a metal such as Si and Sn, which exhibits a high charging/discharging capacity in comparison to a carbon material and allows electrochemical alloying, as the anode active material.
However, the metallic anode active material is easily cracked or made into powder due to its serious change of volume accompanied with charging or discharging, and thus a secondary battery using such a metallic anode active material suffers from a rapidly deteriorated capacity according to charging/discharging cycles and a short cycle span.
Therefore, to prevent such problems, there have been recently made many endeavors to use a metal oxide such as SiO as the anode active material. In particular, SiO may be used as the anode active material solely or together with another material such as a carbon material.
However, in order to utilize SiO as the anode active material, several problems should be solved. Representatively, a manufacturing cost should be lowered by shortening a manufacturing time of SiO and allowing mass production. However, SiO manufacturing techniques proposed until now have a limit in mass-producing SiO. Therefore, there is needed to develop a new SiO manufacturing technique.